RATIO AND PROPORTION PART II

PROPORTIONAL DIVISION

Proportional division is about sharing something in a given ratio. The ratio tells you how to do the sharing. To divide something in a given ratio:
1. Find the total number of parts for the ratio.
The ratio x:y gives (x + y) parts. The ratio x:y:z gives (x+y+z) parts and so on.....
2. Find what one part is. Thus the part corresponding to x,y or z. The share corresponding to x can be found by using the fraction ^x⁄ _x+y+z
Similarly the share corresponding to y is given by the fraction ^y ⁄ _x+y+z etc.
The something can be a number, an amount of money, a measurement etc.

EXAMPLE

A green pain mixed from a blue and yellow paint in the ratio 3:5. How much o each colour is needed to make 40 litres of this paint?

SOLUTION

The ratio 3:5 gives (3+5)= 8 parts. 40 litres of green are needed.
Blue paint needed= ³⁄₈ × 40 litres = 15 litres.
Yellow pain needed = ⁵⁄₈ × 40 litres = 25 litres

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ASSIGNMENT

The expenditure on roads , school and water supply are in the ratio 7:15:2. If the expenditure on roads is $28 million, find the expenditure on
1. schools
2 water supply
3. What is the budget for these three projects?
4. The cost of maintaining libraries is $900,000 and this is met from the expenditure on schools. What percentage, correct to 3 significant figures, of the expenditure on schools is spent on maintaining libraries?